Many industrial fields require the gripping of tubular members so that they may be axially-rotated or secured against rotation, most notably in order to assemble and disassemble threaded connections. The oil and gas industry relies heavily on such assembly and disassembly, especially in oil and gas exploration, where a single well can include tubular strings that are thousands of feet in length. These strings include individual tubular members (referred to as “joints”) that are threaded together, end-to-end via male and female connectors.
Tongs have been developed to grip tubular members in order to facilitate the repetitive task of assembling and disassembling threaded connections. One type of tong, commonly called a power tong, rotates a first threaded tubular member on its axis, while another type of tong, commonly called a backup tong, secures a second, mating tubular member against rotation.
As wells become increasingly deeper, tubular strings in turn become increasingly long and heavy, subjecting the tubular members and connections to substantial axial loading, as well as to extreme internal and external pressures. Additionally, the liquid and gaseous production fluids transported from the subterranean reservoir to the surface through these tubular strings can be corrosive. To provide a long-life well structure in situations where the produced fluid is known or expected to contain corrosive constituents, the tubular members are selected from a range of corrosive-resistant alloys (CRAs). In order maximize corrosion resistance, even superficial damage to the tubular members is avoided. Mechanical damage to the surface of the tubular members, which may be imparted onto the tubular members during the installation process, has the potential to lead to premature failure of the tubular members in the well. Considering the high cost of CRA tubular members, not to mention the cost, time, and danger associated with failure of the tubular string in a well, care is taken to prevent damage to the tubular members during assembly and disassembly of the threaded connections.
Various mechanical gripping devices for tubular members are known, most of which rely on hardened gripping teeth to penetrate the outer surface of the tubular member to assure a grip sufficient for imparting the high torques necessary to achieve tight, leak-proof connections. Other gripping devices utilize smooth cam gripping surfaces or smooth-faced jaws with frictional material applied to the contact surface to grip the tubular members. There are disadvantages, however, associated with these particular gripping devices, namely that they sometimes cause surface or structural damage to the tubular members.
Accordingly, other devices for gripping tubular goods have been developed, which avoid surface damage or structural deformation. Once such device is a Fluid Grip device, in which an inflatable bladder-like structure grips the tubular members. In contrast to mechanical gripping devices with cam-activated jaws and dies, the Fluid Grip utilizes the introduction of hydraulic fluid flow and pressure to the mechanism to inflate elastomeric bladders to establish a gripping engagement between a rigid outer housing that encases the elastomeric bladders and a tubular member. Further, the rigid outer housing is secured to the main rotating gear of a power tong. When utilized in this manner, a power tong equipped with a Fluid Grip is capable of applying a substantial clamping force that can be used to grip and rotate tubulars for the purpose of making up threaded connections.
Currently, the mechanisms used to control and transmit fluid to the Fluid Grip housings require manual interaction, which presents personnel safety issues. For example, the Fluid Grip housing latch and tong door are manually manipulated, endangering rig personnel. In addition, a pressure release valve generally is manually opened to evacuate the bladders and release the grip, thereby allowing the power tong rotating members to re-establish alignment and facilitate lateral removal of the tool from the tubular. Manual manipulation of the pressure release valve similarly places rig personnel at risk.